The technique of microencapsulation by means of polymerization of Isocyanates, for its use in several fields, including agriculture is very well known for the formulation chemist. Many patents describe microencapsulation by means of isocyanates, prepolymers of isocyanates, urea-formaldehyde resins with polyols and functionalized amines as catalysts. The applicant, as described in EP 1840145 introduced in the wall forming materials of the microcapsules, for the first time, derivatives of glycoluril combined with aliphatic and aromatic isocyanates. That patent, that reflects the closest state of the art of the present invention (of the same inventors), shows a method of microencapsulation in which, in between other novel elements and advantages, the microcapsules have improved properties regarding the better control on the chemical structure of the wall (due to the introduction of glycoluril derivatives) and improves the toxicology associated to production, due to the fact that partly the isocyanates are substituted by the less toxic glycoluril derivatives and the quantity of isocyanates is lower.
In the same way, due to the lower reactivity of the glycoluril derivatives, the microencapsulation reaction described in EP 1840145 is easily controlled with respect to the state of the art prior to EP. The present invention improves the formulated products resulting from the invention EP 1840145, with regard to several compounds, and it is novel in the present invention the combination of glycoluril resins with urea resins, without using catalysts of the type metal dibutyl-laureates or amines or polyols. At the same time, in the present invention we use a determined type of surface active agents that improves notably the stability at long term, while this combinations are clearly non obvious in front of any prior art known by the authors at the view of the almost infinite combinations possible to be made of polymers or oligomers or monomers that are wall forming materials, and at the same time that during the process, a determined type of surface active agent is used in order to obtain a good emulsion that yields a mean particle size lower than 5-6 pm, and moreover, improves the properties of the final formulation in which such microcapsules are contained regarding agglomeration and bleeding, as this is the effect of the surface active agent CoP-1 described elsewhere in this document.
The inventors of the present invention have continued to research in processes with better control of reaction since the realization of the invention EP 1840145. It must be noted that an industrial microencapsulation reaction is an “all or nothing” reaction, namely, that if a phase inversion takes place, or the particle size is not appropriate, the whole production lot (e.g. 500 to 20000 kg) must be sent to waste, with the losses of the materials used in such reaction and the costs of waste-burning. Then, small advances in the control of reaction have a high economical impact, since such advances may reduce the percentage of failed miroencapsulations' reactions from 0.5% to a 0.1%, with a high economical impact. This is the case of the present applicant: the inventors have observed in their pilot plant (of 50 kg per batch) during 2 months such mentioned reduction in failed reactions -for several compounds to be microencapsulated-, that reduction of failures due to change the method described in EP 1840145 to the method described in the present invention. Together with this improved control of reaction, the present invention improves (with regard EP 1840145 and all microencapsulation processes published or patented known for the inventors) another problem than may occur as is the bleeding and the agglomeration of microcapsules. The latter improvement over the prior art is specially relevant for the shelf-life of formulated product at long term.
Among the problems that may appear in formulations containing microcapsules is the appearance over time of a phase separation (a part of the oil used during the process is separated as a layer on the top of the external water phase of the microcapsules), generally known as “bleeding”, as well as problems associated with the agglomeration of the microcapsules over time. The present invention deals with formulation of microcapsules that are improved with respect other ones, for periods over two years, In terms of bleeding and agglomeration, apart from the improvement in the control of the reaction due to the use of polyurea “blocks” as wall forming materials (combined with glycoluril resins) instead of the use of the initial use in the reaction of isocyanates in monomer, oligomer (prepolymers) isocyanates, as is the state of the art.
Another problem not solved by the state of art is the optimization of the microencapsulation process in reference to the ability to control the speed of reaction in those cases wherein compounds may intervene in the formation of the polyurea wall during the microencapsulation reaction, in particular compounds having groups R—CO—N—R′ being R and R′ any moiety), as it is the case for the agrochemical compounds with carboxamide groups. While EP 1840145 provides an improvement in this respect (by using less reactive glycoluril compounds compared) over the prior art of EP 1840145, in the present invention one of the improvements is that we combine specifically a certain type of wall forming materials and a dispersant/surfactant (surface active material) of the type CoP-1 to create microcapsules for the special case of compounds with at least a carboxamide group, as is the case of sulfonylureas and other agrochemicals. For this compounds with carboxamide groups, it is observed that by the use of the present invention, we obtain the benefits of incorporating glycoluril groups to the polyurea wall (being this polyurea the result of the reaction of urea-formaldehyde resin and not with isocyanates as is the case in EP 1840145) and at the same time we obtain a better control of the reaction (apart from improving the bleeding and agglomeration characteristics of the formulated carboxamides). It is noted that EP 1840145 it can also be prepared formulations of compounds with carboxamide groups; however in two reactions in an industrial reactor of 200 liters happened an overheating and rapid evolution of CO2 with consequent loss of emulsified phase due to spilling from the top of the reactor. While this problem may be solved by a different design in the reactor (to allow the elimination of the CO2 by a more efficient way), in the present invention, the inventors have seeked a solution that goes beyond an obvious solution for this problem. At the end, the present invention has resulted in surprising benefits over those faced by the inventors, and provides a microencapsulation process and microcapsules wherein the reaction is better controlled and further, the properties of the formulation (regarding bleeding and agglomeration at long term) are improved, and also the invention may be used for compounds that do not have carboxamide groups (since the improved properties of the formulation still apply). Although the problem that lead the inventors to invent the present invention had its origin in the microencapsulation of boscalid and then prochloraz, we have found that the invention may be applicable to other compounds without carboxamide groups, although it is declared that the best improvement (but not the only one) is referred to the control of the reaction for carboxamide groups.
Noteworthy, the present invention is perfectly applicable for any Industrial field in which carboxamide compounds are to be microencapsulated, as might be flame retardants, phase transfer materials, pharmaceuticals, cosmetics, etc. We refer hereinafter to the field in which we have our most interest, namely, in the agrochemical field.